Thermal Pane Roof Vent Cover by Hengs®. Heng's Industries USA, LLC is a premier manufacturer supplier of quality recreational vehicle and marine products. We provide a diverse series of quality products ranging from vents to sealants to affordable furniture supplying distributors throughout the United States and Canada. We are proud to offer the highest quality products including: Vents, Range hoods, Converters, Sealants, Portable Toilets, Furniture.